The invention refers to a device to form drops from viscous, flowing masses that are arranged in a container with at least one steel wall equipped with several rows of openings, and that can be cyclically extruded in drop form through one row of openings at any given time, as soon as this row, during movement of the wall, comes into alignment with an aperture exit area that is not rotating along with the wall, whereby for heating the masses remaining in the openings, at least one heating installation is associated with the wall and/or the exit area.
Devices of this type are known (DE-PS 28 53 054 and DE-PS 29 41 802). These devices equipped with rotating outer tubes have the considerable advantage that they can form tablets fairly easily and at a high rate from masses that could otherwise only be deposited in layers on cooling conveyors and that would then cause environmentally harmful dust development when being broken up into pieces.
It is also known that due to their viscosity, the drops emerging from the rows of holes to then become tablets on the cooling conveyor form threads connected to the mass remaining in the openings. If they do not tear off in timely manner, these threads then became deposited, during the continuing rotation, on the periphery of the rotating container tube. Efforts have been made to return non-deposited mass back into the container. One such proposal involves arranging eccentric gaps in the container, through which the mass is sucked back in. Also known are guides adjacent to the container periphery, which are heated and with the help of which the material adhering to the periphery is pressed back into the drip openings. In any case, a precondition is that the mass moved back should be sufficiently reheated to be flowable enough for a return procedure and for the renewed drip procedure.
The rotating tubes have generally been made of stainless steel for reasons of corrosion and wear. Since this material has very poor sliding properties, however, a gap was usually created between the stationary inside container and the rotating tube. Since the heating of such rotary formers takes place by heating the inner stationary body, with many products it occurs that the outer rotating container and the remaining masses adhering to it cool off excessively, in such a way that the threads stretching from the drops deposited on the cooling conveyor to the rotating outer surface of the container do not always tear off and onto the drops formed. A flawless, dust-free granulation is therefore not always possible with such materials.
It has also been shown that the temperature increase in the inside of the stationary body cannot be set as high as desired in order to sufficiently heat up the rotating outer tube. In addition, materials must also be worked that cannot be heated too high due to danger of explosion. This restricts the use of heaters arranged outside the rotating tube as well.
Similar problems can also occur with other granulating installations where the viscous material is extruded between an extrusion roller arranged inside a rotating roller body and the outer roller, with the help of serrated slats attached to the inside periphery of the outer roller and the outer periphery of the extrusion roller (DE-OS 36 15 677), or in which a rotating belt provided with openings is attached to a stationary nozzle lip (DE-PS 33 27 479).
The task of the present invention is thus to design a device of the type mentioned in the beginning in such a way that heating the moving wall to the required degree is possible with no danger of damaging the product through overheating or of reaching its fire point or the ignition temperature.